Concentration of aliphatic acids



rial v l This invleiitioniziclctesljtoa remix ofi'lowen fatty .:acids;;panticulanc aceticacirt. ltx-islespew cially;concerned;.witlr..the;recovery-oi? such acids," together withcelluloseesters, from solutionsiofi cellulose esters in; the; said: acids, e. y e; the; recovcry of cellulose acetate,'andiaceticga'cidzfxcimsoluw tions of cellulosepacetatejn acetic .acid;-or ex- I amplei those obtained.- by thezacetylation" of ce lf lulose with; acetic anhydndetin" the; presence of:

sulphuriceltacidi .'I'I-1elnyention will: be described more particularly m relation-tottheitreatment ofi suchisolutions'z A common method iof iisolating', cellulose iacetaite: 1

and recovering acetic acid: inrjfconcentmtedfifom fromtso lutions c1; cellulose: acetate i'ni acetic; I is; tou precipitatethe cellulose acetate by the} ace than of; anl'aqueous-t-liquid; and-them aften separatsulphate; lmthe action ofs'ammonim orcammonium' ing thelprecipitatedr cellulose acetate; to! extract be: employed in relation. to: the i ainounti of acid recovredv can be- 'reduced-venyi greatly ifthe aqueousia'cid,undergoingextrectiori contains am N01)! wing. implication Febiuary 12, 1941, Se-

Nq. 373,63}; 'In Great -BiiitaimMai-ch 5, f

A ubst ril-iahn emr i en e}! boz liei xtenti r ast Q%- besedromtheweiehtso awaten p es t It is preferred to use a proportion of oer-met e,

.ammeniumjsulphate, this; can s.=.;t o;:1 ave:mlthelliquidafmm,

aeidamesent beforeextmct-ion; Q

, l newz pmcess; is,-10f:.-.espe ial: value for; the. o isolation-:02? cenul'cse acetate:fromiacetylation solutionswobtainedi byi. acetylating. cellulosei with v'ecetiQanhYdrideixrjaceticacid-in pnesenceofisuh v huzric: acid: liwmexriaimlyinethe process to i such Y I o0N(iEN"rem x on OF ALIBHATI ACIDSQ,

Wann r-leery emombriage aria Renate Pa e,v -.Spondon, nean Derby, England;..as'signoxs to u Gelmiese. Gcmunaetion of Amemz: w. comma-e i the a ueous: "liquid: on a nin a tic? acid; end

eoilubionaswhiclr may. havesbeeii fflpenedi) the sulphuric acid content-ixcqnventedtowammonimn' acetatewhich be eddedajdirectly tcjthe celg-i lulose acetate solution or included in the precipi-ai tatdon liquid. v13y using ammomwjor-emmcnium acetate; tars destruction i of: the: sulphuric yacidithe fomnationecanlhe: avoided: of: salts:oth;en'fiian:am-. sulpham, oxcofi. acids .oth'en: than acetic mon'iumv sulphate andliti the extraction. ofl theacetic} acidl's disoontinued when a substantial proportion Ora me acetic acid still: a ing izig the aqueousliquim z According i itc -the presenti inventioncellulose acetate is pnec'ipitatedirOm a solution thei eoti infacetic acidgby the action of' an aqueous "solution of ammoniuni sulphate containing" some 1 acetic acid; I and; aftepf separating; the-precipitated cel:

lulo'se ace-ewe: fonly of the acetic 'a/cidiis extracted from-: theaque'ous liquid bysthe meanof a. solvent for acetic acid, .residuakliaqueous liquid heingi thehiusedt as at least 'part 01 a precipitatingiliquid for :the' preclpitation of fu'rthei cellulose acetatel from an acetic acid solution thereof; The extiactlomot a Partonly of the;

acetic acid ccntenb'fof: the -aqueous;'liquidg come. bin'ed lwithl-the presence of the ammonium" sul- 1 abid-,:.-imthegliquldztfi be extmactedion thatxto': be used fortprecipitatiomfoficelluloseracetate;e'

j Whemeellulose:acetatefsolutiomcontainingssul' phuric acidgeareu treated;tasasdescribediabovexthej quantity of: ammonium; sulphate presem'iwili in crease with? each cycle: of operations; unles'sfi'a'.

suitable proportion is: removed frcmtimet'oi time and preferably-at"eachicycle'. -Mo'st; convenient j 131, after extractionofipaiitf.ofii'the a'cetic;acid;a suitable:*portion 'onltherresidual.ammoniumasul phatei solution containing:some waceticl acid: is treait'eclhfort recoveny ofxaceticiacid' and ammo'nie;

'Ihevacetlcacidns conveniently rrecoveredflby extraction with az solvent midi-the ammonia by. dis-" tillation ofthe "residual-liqui'd.:withvlime: c1rother I alkali. 1: The: recovered ammonia: is then avail-5 I able fonzccmbiningrwithgtheisulphuriciacidzofi a" cellulose acetate:'sclutionycontainingthislacidi as describedabcve: :Usuallyfitrisg convenientxto; mix. it with, the; main; bcdy'ofisammoniumi sulphate carried outeso to :of the acetatecsolution-q-toz behreccvered byfextrection wlthta prcportionsofr sclv'ent whiohds ve yniuch' le'ssethanl is: the case when these expeclie'nts a-l e t noteinployedl gAtzthessamia time animonium sul phatev cnntentziQfi theillquidfafter extraction of l tated:cellulose zacetate; 'Th'is washingofqthe ol acetic.acidz fnom' the latterg is *uti1ised in a suelulo'se acetate is':convenientlyaefiectediin counter:- c'aedm'gzoperationlwibhoilfl-expensive dperafion g 'cun entg'that:iestossazythelenimcniumsulphate v suchaas concentr'alti'oniofithe:ammianium:sulphatesolution is ,used to rwa'sh successive portions f;: solution-.onlsolation ofl the mmonium sulphate cellulose acetate-ofiprogressivelyincreasing acetics m-:;sona;mm-. r n acidiccntenti aceti ;"acid eontent ofithea;

1, m m m ml l h t ml' glp e melmz monlum su1p1me :sclutibm is threbygfiincreased solution;containingeicetlc: acid; to be use'd for theprcipitation'ofthe cellulose'acetatea I oni'f romi which and it is thereafter used to precipitate cellulose acetate. The precipitated cellulose acetate, after the washing with ammonium sulphate solution,

is washed with water, the washings being mixed with the ammonium sulphate solution before the latter is used for washing cellulose acetate as mentioned above. Some Water is thereby introduced at eachcycle of operations and can be arranged to compensate for that removed, as de-; scribed above, in the form of ammoniumsulphate solution for recovery of ammonia.

Varioussolvents may be used for the extraction. [They should preferably :be such as do' not dissolve in, or take up waterfrom, aqueous am monium sulphate solutions to a very substantial extent. Their boiling points may be aboveor below that of the acetic acid to be extracted.

' Further their boiling points should preferably differ from that of the acetic acid by somuch that they can be readily separated from the acid by a distillation operation. They maylconsist'of single chemical compounds or mixtures of-com- Pounds.

Examples of solvents suitable for the extraction of acetic acid and having-aboiling point belowthat of "acetic acidare diethyl-"ether; di-

propylether, di-isopropyl ether," ethyl 'acetate and similar volatile-esters of acetic abidflmethylene chloride and ethylene'chloride. 'Particular mention maybe made of the mixtures" of solvents for acetic acid 'with hydrocarbonsg'rnentioned'in U. S. Patent. No. 1,696,432; -A 'suitable mixture is that of diethyl ether with petroleum ether or ethyl acetate with benzene, e. g. a mix-5 ture of 4 parts by volume of ethyl a 6 parts by volumeof benzene; i l i ,7

An example of a suitable solventih'aving 'a boiling point above that *of acetic acid is "amyl acetate.

The extraction l with the solvent is "advantamixture, together with the solvent, thereby facilitating the production of a highly concentrated or even substantially anhydrous acid. I

The process of the invention can also be applied to the isolation of cellulose esters from solutions generally of cellulose esters in lower fatty acids and particularly solutions which have been prepared by esterification of cellulose in presence of a lower fatty acid, for example a solution of cellulose propionate in propionic 7 treated.

Further,

general less advantageously and'particularly so where an esterification solution prepared with the aid of sulphuric acidjas catalystisbein The foregoing inodifications are included in the scope-of the application which also includes broadly the extraction, by means of; a solvent, 7 of acetic orother lower fattyacid froman 'aqu'eous solution thereof containing-L ammonium sulphate or other ammonium-saltin substantial. Proportion;

Having described acetate and acetic acid :flQlll a solution" of cellulose geously effected systematically, a given 'body. 'of I solvent beingused to extract successively a series of acid solutions .of progressively increasing"- concentration. Batchvmethodsflmay be used,

extraction being then' conveniently, effected in a series-of vessels and the 'ex tractg and extracted liquor. being transferred from ?vessel to. vessel,

the extract for extraction ofofurther acid: ofhig her concentration than that :justextracted,

and the extracted liquor for extraction by sol vent containing a smaller proportion of acid thanthat justused for extractionvf i t Again, continuous counterflow extraction may V be used, the solvent: being run'rin counter-current to the aqueous liquor; The'apparatus-may then conveniently take the, form of a column, through which the aqueous acid andsolvent are passed in counterfiow, whichever has the lower specific gravity being introduced atthe -lowerpart of: the column. The liquids are advantageouslyin troduced into the column in ase'ries offifine streamsso as to provide a large surfaceof con-w centratejd can be removedtoasubstantialdegree;

during'the distillation, ,in'the form; of such a,

acetate in acetic. acidsywhich compris'es' pre-J cipitating the,v cellulose acetate ffronfrithe solution by the. actionof anwaqueous solution of ammonium sulphate containing some aceti'c acid;

separatingthe precipitated cellulose acetate, ex:

\tracting apart only of the acetic acid-from the 7 aqueous liquidbyhthe action of a solv'ent' for acetic acid which is."substantially!immiscible with'water; removing; the solventtfrom the ex-:

tract, and using thetresidual aqueousxliquid as at least part. of" ani'aqueousliquid .for. the 2 ,pre-

cipitation of furtherc'ellulose acetate frornnan acetic acid solution thereof;

12. Process for: theirecovery of: aalowerifat ty acid. andailcellulose ester of a lower fatty .acid

from a soluti0nof -the ssaidaester in the lower fatty acid; which comprises -..precipitating,--the cellulose ester from the solution .by :the. action; of an aqueous ,solutionoff-ammonium sulphate containing some of the lowerifattyiacid, 'separating the precipitated ester, extracting: a only of, the lower fatty -acid froms-thexi aqueous liquidby the action of, a solvent therefor which is substantially immiscible; withxfiwater,;jre.-' s moving the solvent from theji extracts-"and using the, residual aqueous liquid as atv least part of an I aqueous liquid for the iprecipitation" of further cellulose ester (from a solution :thereof in the lowerfattyacidQ 3. ;Process for the recoveryrof a lower fatty"; acid and a cellulose ester of-allowerfatty acid from an esterification solution ofxtli'e said ester made by ,esterification of cellulose with a. lower fatty acid ,anhydridein a; lower fatty acid using sulphuric, acid as catalyst, which-comprises pre' cipitating the cellulose, ester from the-solution,

by theqaction Of-anaqueous solution of am monium sulphate containing some" of the lower fattyfacid and sufficient: of pan-"ammonium salt of the lower fatty acid*to convert the sulphuric? acid present into, "ammonium "sulphate, 'separat ing the precipitated ester, extractingianparttonly" of, the lower fattyacid-fromthe aqueous-liquid by the action of; a: solvent therefor which is substantially immiscible with'waterjrem-ovmg the solvent from the extract, and using the residual queousl qu d"aslzat least part of: anaqueous in place of ammonium sulphate other tarnmonium, salts "can be employed, though in ta. masts, what wade-1 si to secure by LettersPatentlisz E J' a '1. Process fortherecovery ofcellulose escapes 7 liquid for the precipitation or further cellulose ester from a solutionthereof in theloweffatty 4."Process for the recovery of 'cellulose acetate and acetic acid'from an acetylation-solution made by acetylating cellulose'withiacetic anhydride in acetic acid'usin'g sulphuric acid as catalyst, which comprises precipitating the cellulose acetate from the solutionby the action of an aqueous solution of ammonium sulphate containing some acetic acid; separating the precipitated cellulose acetate, extracting a part only of theacetic acid from the aqueous liquid by the action of a solvent for acetic acid which is substantiallyimmiscible-with"water,

removing the solvent from the extract, andrusi'ng the residual aqueous liquid as at least part f an aqueous liquid for the precipitation of further cellulose acetate fromian aceticaacid solution I thereof.

5. Process forthe recovery of celluloseacetate and acetic acid from an acetylation solutionmade by acetylating cellulose with acetic anhydride in acetic'acid using sulphuric acid as catalyst, which I comprises precipitating the celluloseacetate from the solution by the action of an aqueous solution of ammonium sulphate containing some acetic acid and sufiicient ammonium acetate to convert the sulphuric acid present into ammonium 'sulphate, separatingthe precipitated cellulose acetate, extracting apart only otfthe acetic acid fromthe aqueous liquid by the action of a solvent for acetic acid which is substantially immiscible with water, removing thexsolvent from the extract, and'usingtheresidual aqueous liquid as i at least part of an aqueous liquid for the precip itation of further cellulose acetate from anzacetic,

acid solution thereof.

h 6. Process for the recovery cellulose acetate t and acetic acid from an acetylation solution made I by acetylatlng cellulose withacetic anhydride in acetic acid using sulphuric acid as catalyst,

which comprises precipitating the cellulose acetate from the solution by the action of an-aqueous 1 solutionof ammonium sulphate containing some v acetic acid and sufficient ammonium acetate to j convert the sulphuric a acid present intoammonium sulphate, the amount of ammonium sulthe extract, and using the residual aqueous liquid as atleast part0: an aqueous llquid for the pre cipitatio'n" ,-'of- ,further, cellulose acetate from an acetic acid'solution thereof.--

- '8.-"Pr ocess for the recovery ofcellulo'se acetate I and acetic acid irom'an acetylation solution made by acetylatin'g cellulose with acetic anhydridein acetic acid using sulphuric acid as c'a;talyst',-which comprises precipitating the cellulose acetatefrom the solution-bythe action of an aqueous solution of ammonium sulphate containing some acetic acid and suflicientammonium acetate to convert the sulphuric acid-present into ammonium suiphate; the amount ofamm'onium sulphate" and ammonium acetate being such that the resultant aqueous liquid contains at least i 10 dr ammoniuml sulphate based on the weight of-j water, extracting from to 90% of the aceti'c a'cid' from the aqueous liquidby the action of a solvent for acetic" acid which is substantially immiscible with waterfremoving the solvent from the extract,fand using the residual aqueous liquid as at least part of an aqueous liquid for the precipi-,

- tation of further cellulose acetate from an acetic acid and sumcient ammonium acetate to convert the-sulphuric acid present into ammonium sul- 35 phate, theamount of ammonium sulphate and ammonium acetate being suchithat the resultant '7 aqueous liquid issubstantially saturated with" ammonium sulphate, separating'the precipitated, cellulose acetate, extracting from 55 to 90% of the acetic acid from the aqueous liquid by the action of a solvent for aceticacid which is substantially immiscible with water, removing the solvent from the extract, and using the residual aqueousliquid as at least part-of an aqueous liquid for the precipitation ofiurther cellulose acetate from an acetic acid solution thereof;

phate and ammonium acetate being such that the L of ammonium sulphate based on the weight of water present, separating the precipitated cellulose acetate, extracting a part only of the acetic} acid from the aqueous liquid by the action of a solvent for acetic acid which is substantially immiscible with water, removing the solvent from the extract, and using the residual aqueous liquid as at least part ofanaqueous liquid for the precipitation' of further cellulose acetate, from an acetic acid solution thereof. v

'7. Process for the recovery of cellulose acetate and acetic acid from an acetylation solution made by acetylating' cellulosewith acetic anhydride in acetic acid using sulphuric acid as catalyst, which comprises precipitating the, cellulose acetate from the solution by the action of an aqueous solution 01' ammoniumsulphate containing some acetic acid and sufiicient ammonium acetate to convert the sulphuric acid presentinto ammonium sulphate, the amount of ammonium sulphate and resultant aqueous'liquid contains at least 10% ammonium acetate being such that the resultant aqueous liquid is substantiallysaturated with ammonium sulphate, separating the precipitated cellulose acetate, extracting'a part only of the acetic acid from the aqueous liquid by the action of a solvent for acetic acid which is substantially immiscible with water, removingthe solvent from 10. Process for the recovery of cellulose acetate and acetic acid from anacetylation solution made i t by acetylating cellulose with acetic anhydride-in acetic acid using sulphuric acid as catalyst, which comprises precipitating the cellulose, acetate from the solution by the action of an aqueous solution of ammonium sulphate containing some: acetic acid and sufilcient ammonium acetate to convert f the sulphuric acid present into ammonium sulphate, the amount of ammonium sulphate and e ammonium acetate beingsuch that the resultant aqueous liquid contains at least 10% of ammonium sulphate based on the weight of water present, separating the precipitated cellulose acetate, extracting from 55 to of the acetic acid from the aqueous liquid by the action of a mixture of benzene and ethyl acetate, removing; the benzene and ethylacetate from the extract, and using the residual aqueous liquid as at least part of an aqueous liquid for the precipitation of further cellulose acetate from an acetic acid solution thereof. I

11. Process for the recovery of cellulose acetate 'andacetic acid from an acetylation solution made by acetylating cellulose with acetic anhydride in aceticacid using sulphuric acid as catalyst which comprises precipitating the celluloseacetate from I the solution by the action of an aqueous solution of ammonium sulphate containing some acetic the sulphur c. .aplsl nr agnt 1mm fi ahevrnhe meant at Lammnmm su phatmagxd ammonium aetate being auchfihat: the: mam:

aqueous: liquid. is; substantial-1y .sa mieda with sulphate,mwmfinathe. mt smitaied the) acetic; acid from .thaaa'qktwust liquid by: the actiongof a, nuxture'ot benzane amt ethxkacetate; mmoving the benzene and ethyl acetatefrom the extracts, and using the. residual agq equs for the precipitation of vvfurtlmr j cellulose aeetate' fmmmvaceticaacid solution thereohq,

12., Bmqess for. the, extraction. of, meme. a id from: aqueous, solutions thereqf; whim, cnmprises forming ,at, least; 10%. miaam rrmvmxnzn..s1=1lf.a1'

based onthe weight, of the water present, in said muequs-solutiongof 'aceticacid and extracting I cellulose" acetate, extractin ffm fi to 9.0% of thiem ution with .m l sntzfior; (3mm whiszh 1 subs ant a ly immis ible with. wate .sufl eis solvent being employed vtovextract; 55 .to 90% 93 thaapetimacidmresgnt and then remqvingjhe se ls/lent 20m the ext ctv ,-3.2, Rmqe imr the; e tractionof alz ti -i id .fmm aqueous summons thereqn whi h, comprises iomama. 'suflieient ammonium sulfatam said somentirom the extract l V WALTER :GRCOiaiRibn. a

" RONALD PAGE. I 

